The major objective of this project is to determine the minimal chemical composition and mechanism of action of microbial components responsible for immunopotentiation and immunosuppression. In the past year, attempts were made to identify by fractionation and evaluate by chemical and biological analysis components from Corynebacterium parvum and Mycobacterium bovis (BCG) that are efficacious antitumor agents and/or inhibitors of cell-mediated immune responses. Techniques are being employed to assess the cellular nature of the differentially affected biological responses induced by microbial fractions.